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Diffstat (limited to 'src/libposixplz/doublefork.c')
-rw-r--r--src/libposixplz/doublefork.c51
1 files changed, 51 insertions, 0 deletions
diff --git a/src/libposixplz/doublefork.c b/src/libposixplz/doublefork.c
new file mode 100644
index 0000000..6038a9f
--- /dev/null
+++ b/src/libposixplz/doublefork.c
@@ -0,0 +1,51 @@
+/* ISC license. */
+
+#include <sys/wait.h>
+#include <unistd.h>
+#include <errno.h>
+#include <skalibs/uint64.h>
+#include <skalibs/allreadwrite.h>
+#include <skalibs/djbunix.h>
+#include <skalibs/posixplz.h>
+
+pid_t doublefork ()
+{
+ char pack[8] ;
+ int fd[2] ;
+ pid_t child ;
+ if (pipe(fd) == -1) return -1 ;
+ child = fork() ;
+ switch (child)
+ {
+ case -1:
+ {
+ fd_close(fd[1]) ;
+ fd_close(fd[0]) ;
+ return -1 ;
+ }
+ case 0:
+ {
+ pid_t pid ;
+ fd_close(fd[0]) ;
+ pid = fork() ;
+ switch (pid)
+ {
+ case -1: _exit(errno) ;
+ case 0: fd_close(fd[1]) ; return 0 ;
+ }
+ uint64_pack_big(pack, pid) ;
+ _exit((allwrite(fd[1], pack, 8) < 8) ? errno : 0) ;
+ }
+ }
+ fd_close(fd[1]) ;
+ {
+ uint64_t grandchild = 0 ;
+ int wstat ;
+ if (allread(fd[0], pack, 8) < 8) grandchild = 1 ;
+ fd_close(fd[0]) ;
+ wait_pid(child, &wstat) ;
+ if (grandchild) return (errno = WIFSIGNALED(wstat) ? EINTR : WEXITSTATUS(wstat), -1) ;
+ uint64_unpack_big(pack, &grandchild) ;
+ return (pid_t)grandchild ;
+ }
+}